When a patient requires the use of an intravenous (IV) drip for the introduction of various fluids into his or her body, it is common for a physician to prescribe a set flow rate in cubic centimeters per hour (cc/hr). A health care provider, usually a nurse, sets this rate manually by turning a small set screw which is located on the IV tubing connected to the patient. The nurse uses his or her best judgment to manually count the number of drips passing through the drip chamber per unit of time and then estimates the drip rate. The nurse must then mentally convert the drip rate measured in drips/minute to a flow rate measured in cc/hr. If the estimated flow is higher or lower than desired, the nurse adjusts the set screw, recounts the drips per unit of time, and re-estimates the flow rate. This process continues until the nurse is satisfied that the prescribed flow rate has been achieved. Naturally, such a process is susceptible to human error. Additionally, it is common for the set flow rate to vary from the prescribed flow rate as the patient moves into different positions. For example, if the patient rolls over and puts pressure on the drip tube, the flow rate may significantly decrease. The nurse will intermittently monitor the flow rate over his or her shift; however, he or she has no way of accurately knowing the total infused fluid over any interval of time apart from the beginning of the shift. Even the latter estimation is subject to error as the intravenous fluid bag is often partially full at the beginning of a shift (i.e., time point zero) and the volume of the intravenous bag at that point in time cannot be measured with precision. If the estimated starting volume is erroneous, then any subsequent estimate of total infused volume will be inaccurate.
Some IV systems include a monitoring device that activates an alarm if the actual drip rate deviates significantly from the prescribed rate. An example of such an alarm is disclosed in U.S. Patent Application Publication No. 2004/0171994 to Goldberg et al. This alarm only causes the nurse to be made aware that the actual drip rate has significantly deviated from the prescribed drip rate. Additionally, the device does not translate the drip rate to a flow rate measured in cc/hr. Once the alarm has been detected, and in order to re-establish the prescribed flow rate, the nurse would have to manually adjust the set screw, count the number of drips per unit of time, estimate the rate, and repeat the process until he or she is satisfied that the flow rate is back to its prescribed value. This process is further complicated in a dark room (e.g. at night) since the nurse would need to use a flashlight to count and monitor the drips, making the entire process more cumbersome and prone to error. It is well-known that the flow rate varies with patient positioning and other patient related factors. It is entirely possible that the flow rate could be at the prescribed rate at the time of the intermittent check by the nurse and be significantly higher or lower at other times. The nurse has no way of knowing of these variances apart from viewing the intravenous fluid bag and estimating the change in volume. As noted, this estimation is subject to measurement error, and is generally not calculated more than once or twice per 8 hour shift. The resultant time lag and/or error in determining a deficiency in intravenous fluid administration could be seriously detrimental to patient care.
It is an object of the present invention to obviate or mitigate at least some of the problems and limitations in administering intravenous fluids.